430 Butler: The western American birches 



rate teeth of the latter readily separate the two. The type is D. T, 

 MacDougars 66j, collected near Rost Lake, Montana, and is ap- 

 parently rare. 



8. Betula Sandbergi Britton, Bull. Torrey Club 31: 166. 1904 



A shrub or shrub-like tree with dark reddish-brown bark, not 

 separable into layers ; lenticels not conspicuous ; branchlets finely 

 pubescent but not glandular-resiniferous, coarse, greenish, becom- 

 ing gray and red-brown, covered with a bluish bloom ; leaf-blades 

 up to 6 cm. long in the type specimen, 3-4 cm. in the Rocky 

 Mountain form and 12-22 mm. wide, thick, firm, dull bronze- 

 green above, paler and sparsely hairy beneath, slightly resinous, 

 rhombic-ovate ■ or oval, acute at both ends, margins somewhat 

 thickened, coarsely and irregularly serrate or dentate, veins 4 or $ 

 pairs ; fruiting aments 2-3 cm. long, slender-stalked ; bractlets 

 about 4 mm. long, nearly as wide, pubescent, middle lobe mostly 

 triangular, obtuse or acute, longer than the ascending, rounded, 

 lateral ones ; samara 3-5 mm. wide, wings broader than the more 



or less puberulent nutlet [Figure 8.] 



This small tree-like birch is readily distinguished by its coarse 

 thick rhombic leaves and pubescent, often glabrous, but not gland- 

 ular-resiniferous branchlets. It frequents swampy places and re- 

 sembles Betula fontinalis in habit and growth but is readily dis- 

 tinguished from that species by the leaves and branchlets. The 

 leaves are larger and more coarsely toothed than those of B. 

 Elrodiana, the bractlets and fruiting aments are quite different, 

 and the latter remains a low shrub, not assuming a tree-like form. 



The type locality is Hennepin Co., Minnesota. It has been 

 found in Saskatchewan and in Montana, being apparently rare. 



9. Betula fontinalis Sarg. Bot. Gaz. 31 : 239. 190 1 



I 



Shrub-like, forming clumps similar to those of some of the 

 willows and reaching from four to eight meters in height, often 

 assuming tree-like proportions; bark smooth, shining dark reddish- 

 brown or bronze with pale conspicuous lenticels, not separable into 

 layers or peeling on the surface ; branchlets densely glandular- 

 resiniferous, slender, graceful, somewhat pendulous; leaf-blades 

 2-4 cm. long and nearly or quite as wide, often larger on sturdy 

 young shoots, broadly ovate to suborbicular. with acute apex and 

 mostly rounded base, sharply and often doubly serrate, thin, firm, 

 'bright green, resinous, with 3-5 pairs of slender veins; fruiting 

 aments 2-3 cm. long, 5-10 mm. thick; bractlets pubescent, ciliate. 



